Wash the fish, dab dry and cut into about 4 pieces. Sprinkle with lemon juice. Peel onions and cut into rings. Peel and wash the carrots. Brush the potatoes vigorously under water. Cut both into thin slices
Heat the oil in a large frying pan. Fry the onions and potatoes for 6-8 minutes. Season with salt. Add carrots, pour 100 ml water. Bring to the boil, cover and stew for about 5 minutes
Coarsely crush the peppercorns in a mortar. Finely crumble the toast. Knead with butter and pepper
Arrange the vegetables in 2 small or 1 large greased casserole dish. Salt the fish and place on top. Spread the pepper mixture evenly on top. Bake in the preheated oven (electric cooker: 225 °C/circulating air: 200 °C/gas: level 4) for 20-25 minutes, garnish